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A study was conducted to determine the effect of including expeller-extracted canola meal (EECM) in diets for broilers on performance, thyroid gland size, liver and kidney sizes, blood serum concentration of triiodothyronine and tetraiodothyronine, hemoglobin content in blood, hematocrit, and histology of liver and kidney. A total of 200 male broiler chicks (1 d old) were divided into 40 groups of 5 birds balanced for BW and fed 5 diets in a completely randomized design (8 groups/diet) from d 1 to 21 of age. The diets were a complete corn-soybean meal-based basal diet with 0, 10, 20, 30, or 40% of EECM. Diets were formulated to have the same ME, CP, Ca, nonphytate P, and standardized ileal digestible Met and Lys contents. The EECM contained (% of DM) 37.8% CP, 0.74% Met, 2.14% Lys, 1.62% Thr, 1.61% Val, and 7.64 μmol/g of glucosinolates. An increase in dietary level of EECM from 0 to 40% resulted in a linear decrease in feed intake (P < 0.001) by 4.8 g/21-d period for each 1% increase in EECM and in BW gain (P < 0.001) by 6.0 g/21-d period for each 1% increase in EECM. However, dietary EECM linearly increased liver weight relative to live BW (P < 0.001) and serum tetraiodothyronine concentration (P = 0.019). An increase in dietary level of EECM from 0 to 40% did not result in a significant increase in kidney weight relative to live BW. There was no effect of EECM on heart and thyroid gland weights relative to live BW or on the blood hemoglobin content, hematocrit, and serum triiodothyronine concentration. In conclusion, an increase in dietary level of EECM resulted in reduced growth performance and may interfere with liver function, likely because of increased dietary concentration of glucosinolates. Thus, the amount of EECM included in broiler diets should be based on the desired growth performance and the cost of the EECM.
Woyengo et al. (Tue,) studied this question.